<font color="#888888">Dear Sreekar Guddeti</font>, if you want to calculate a constrained magnetization with antiparallel direction between the atom 2 and atom 8, you must to put the "starting_magnetization" tag with opposite value, for example:<br>
<br> starting_magnetization(2)= 0.3091,<br> starting_magnetization(8)= -0.3091,<br><br>best wishes<br><br>PhD stud. Arles V. Gil Rebaza<br>Instituto de Física de La Plata<br>Argentina.<br><br><div class="gmail_quote">
2011/8/25 sreekar guddeti <span dir="ltr"><<a href="mailto:colonel.sreekar@gmail.com">colonel.sreekar@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Respected Sir/Madam,<br>1. I would like to perform a constrained magnetization calculation for a system, whose unconstrained spin polarized calculation gives an antiferromagnetic state, to converge at the ferromagnetic state.<br>
2. The system is a zigzag graphene nanoribbon(<cite><b><a href="http://en.wikipedia.org/wiki/Graphene" target="_blank">http://en.wikipedia.org/wiki/Graphene</a></b><b></b></cite><span></span>) and I would like to flip the atomic moment at one of the edge site and constrain both the edge site moments.<br>
3. I calculated the antiferromagnetic edge site moment using PDOS calculation. I used 'lambda' parameter to constrain the moments.<br><br>4.Questions: Is 3) the right way to do it? If yes, what should be value of lambda? I used lambda =1 and the scf output (given below) is disturbing... I would like to ask what does "constrained moment : -20.000000" mean and why is the constrain energy so high. If it is not the right way, I would be grateful if you could suggest an alternative.<br>
<br>Thanking you,<br>Yours sincerely,<br>Sreekar Guddeti<br>Undergraduate (5th year)<br>Engineering Physics<br>IIT Bombay<br>India<br><br>PS: The system namelist for scf calculation and the sample output are given below and the complete input file is attached. <br>
<br><br>--------------------------------------<br>...<br> ==============================================================================<br> atom number 15 relative position : -3.5000 6.0622 0.0000<br> charge : 0.983302<br>
magnetization : 0.000256<br> magnetization/charge: 0.000260<br> constrained moment : 0.309100<br><br> ==============================================================================<br><br> ==============================================================================<br>
atom number 16 relative position : -3.0000 5.7735 0.0000<br> charge : 1.783674<br> magnetization : -0.385046<br> magnetization/charge: -0.215873<br> constrained moment : -20.000000<br>
<br> ==============================================================================<br>...<br>...<br><br><b>constraint energy</b> (Ryd) = 6095.83663339<br clear="all">---------------------------------<br><br><br><br>--------------------------------<br>
&SYSTEM<br> ibrav = 12,<br> celldm(1) = 4.608737,<br> celldm(2) = 12.0,<br> celldm(3) = 10.0,<br> celldm(4) = -0.50,<br> nat = 18,<br>
ntyp =10,<br> starting_magnetization(2)= 0.3091,<br> starting_magnetization(8)= 0.3091,<br> occupations='smearing',<br> smearing='gauss',<br>
degauss=0.01,<br> nspin=2,<br> constrained_magnetization='atomic'<br> lambda = 1<br> ecutwfc = 50.D0 ,<br> report = 2<br>
<br> /<br><br><br>-- <br><font color="#888888">Sreekar Guddeti<br><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>###---------> Arles V. <---------###<br>